The alkali-aggregate reaction and blast-furnace slag effect in high-strength concrete were studied in this paper. From the results of this study, it is possible to draw the following conclusions : (1) In high-strength concrete, because of high alkali content, the possibility of alkali-aggregate reaction is much higher than conventional concrete. (2) The occurrence of large expansion can be prevented by using nonreactive aggregate, which has been judged according to the mortar bar and chemical method's as specified in JIS A 5308, in high strength concrete. (3) The replacement of cement by 30% of blast-furnace slag and using low alkali cement can prevent the alkali-aggregate reaction from causing large expansion in high-strength concrete.
